Rukia might also interact with Naruto. She's kind - hearted and might see Naruto's potential. She could be the one to first notice Naruto's situation and try to bridge the gap between him and the rest of the Soul Society. For instance, she could introduce Naruto to some of the more open - minded Soul Reapers.
Iruka could be one. He has always believed in Naruto from the start. Also, Jiraiya might be another. He was Naruto's teacher and had a deep understanding of Naruto's potential. And Kakashi could also support him. He has seen Naruto grow and might recognize his sage powers even when others don't.
Iron Man is another candidate. Tony Stark's technology and Naruto's ninja techniques could be a great contrast. They could learn from each other. Stark might be interested in Naruto's chakra - based powers and try to replicate them in some way, while Naruto could be amazed by Stark's high - tech gadgets.
Obviously Naruto himself would be a main character. He's the focus of the 'neglected' aspect and the 'king' idea probably revolves around him. Sasuke might also be a significant character. His relationship with Naruto could be very different from the original. Since Naruto is neglected, Sasuke might be in a more powerful position within the village, which could create a lot of tension between them.
Well, it might be about Naruto being in the Soul Society world and being neglected. Maybe he's not given proper training or recognition because he's an outsider. He could be struggling to prove himself among the Soul Reapers.
Kakashi could also play a role. He has been Naruto's mentor for a long time. So, he might have some mixed feelings about Itachi adopting Naruto. He could be suspicious of Itachi's motives at first but then gradually come to understand Itachi's positive influence on Naruto. Their interactions could be really fun to read about, especially when Kakashi tries to give Itachi some advice on how to handle Naruto's wild nature.
He would likely interact with the Dragonborn. They could have an interesting exchange of skills, with Naruto showing off his Rasengan and the Dragonborn demonstrating shouts. He might also meet the various Jarls in the different holds, trying to understand their leadership styles which are different from the Hokage in Konoha.
In this fanfiction, Naruto will surely interact with his friends who might be trying to break him out or at least communicate with him from the outside. Inside the prison, he'll encounter inmates with diverse personalities. There could be a wise old prisoner who imparts some valuable wisdom to Naruto. Also, there may be a group of inmates who form a sort of gang within the prison, and Naruto has to either fight them or make peace with them depending on the situation. And of course, there could be a mysterious figure who seems to know more about Naruto's presence in the prison than he himself does, and Naruto will have to figure out this person's motives and identity.
Obviously, Nagato himself would be the main character interacting with Naruto. He would be like a mentor or a guardian figure in Naruto's life.
Definitely the Teen Titans. Robin would be interested in Naruto's strategic mind and combat skills. Starfire might be fascinated by Naruto's unique culture. Beast Boy and Naruto could bond over their fun - loving natures. And Cyborg would be intrigued by Naruto's chakra - based abilities compared to his technological ones.
Well, Lucy would be likely to interact with Naruto. She's friendly and curious, so she'd probably be one of the first to approach Naruto and try to understand where he came from. Gray is also a candidate. His cool - headedness (pun intended) would contrast with Naruto's more energetic personality. And of course, Makarov, the guild master. He would be interested in Naruto's abilities and might offer him a place in the guild or give him some tasks to prove himself in the Fairy Tail world.